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| author | Frederic Weisbecker <frederic@kernel.org> | 2021-05-27 13:34:41 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-05-31 10:14:49 +0200 |
| commit | f268c3737ecaefcfeecfb4cb5e44958a8976f067 (patch) | |
| tree | 895c3ffc8d716b3d00851b569eb183f73a95d9fc /kernel/entry | |
| parent | 02da26ad5ed6ea8680e5d01f20661439611ed776 (diff) | |
| download | lwn-f268c3737ecaefcfeecfb4cb5e44958a8976f067.tar.gz lwn-f268c3737ecaefcfeecfb4cb5e44958a8976f067.zip | |
tick/nohz: Only check for RCU deferred wakeup on user/guest entry when needed
Checking for and processing RCU-nocb deferred wakeup upon user/guest
entry is only relevant when nohz_full runs on the local CPU, otherwise
the periodic tick should take care of it.
Make sure we don't needlessly pollute these fast-paths as a -3%
performance regression on a will-it-scale.per_process_ops has been
reported so far.
Fixes: 47b8ff194c1f (entry: Explicitly flush pending rcuog wakeup before last rescheduling point)
Fixes: 4ae7dc97f726 (entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point)
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20210527113441.465489-1-frederic@kernel.org
Diffstat (limited to 'kernel/entry')
| -rw-r--r-- | kernel/entry/common.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/entry/common.c b/kernel/entry/common.c index a0b3b04fb596..bf16395b9e13 100644 --- a/kernel/entry/common.c +++ b/kernel/entry/common.c @@ -5,6 +5,7 @@ #include <linux/highmem.h> #include <linux/livepatch.h> #include <linux/audit.h> +#include <linux/tick.h> #include "common.h" @@ -186,7 +187,7 @@ static unsigned long exit_to_user_mode_loop(struct pt_regs *regs, local_irq_disable_exit_to_user(); /* Check if any of the above work has queued a deferred wakeup */ - rcu_nocb_flush_deferred_wakeup(); + tick_nohz_user_enter_prepare(); ti_work = READ_ONCE(current_thread_info()->flags); } @@ -202,7 +203,7 @@ static void exit_to_user_mode_prepare(struct pt_regs *regs) lockdep_assert_irqs_disabled(); /* Flush pending rcuog wakeup before the last need_resched() check */ - rcu_nocb_flush_deferred_wakeup(); + tick_nohz_user_enter_prepare(); if (unlikely(ti_work & EXIT_TO_USER_MODE_WORK)) ti_work = exit_to_user_mode_loop(regs, ti_work); |